CN101077487A - Fly ash charcoal-removing parallel plate electrostatic separator and friction charged electrostatic field sorting process - Google Patents

Abstract

The invention relates to a parallel plate electrostatic separator for fly ash decarbonization and a triboelectric electrostatic field separation process, belonging to the technical field of mineral separation. The sorting process consists of three parts: feeding device, parallel plate electrostatic separation chamber, and product collecting device. The feeding device is mainly composed of an electromagnetic vibrating feeder and a pneumatic transmission pipeline to form a fly ash dry powder material feeding device; after the dry powder material is sorted by a parallel plate electrostatic separation chamber, coal-fired fly ash, residual carbon particles and Three kinds of separation products of intermediate materials; coal-fired fly ash products and residual carbon particle products are collected by the product collection device composed of cyclone and bag collector, and the final fly ash products and residual carbon products are obtained respectively. The intermediate products are returned to the parallel plate electrostatic separation chamber for reselection. The process of the invention is a dry physical separation process, which does not require slurry preparation and chemical addition, no waste water generation, and no dehydration filter device. Therefore, compared with wet separation processes such as flotation separation, the process is simple and the operation cost is low.

Description

Parallel plate electrostatic separator for fly ash decarbonization and triboelectric electrostatic field separation process

technical field

The invention belongs to the technical field of mineral separation, and provides a parallel plate electrostatic separator for fly ash decarbonization and a triboelectric electrostatic field separation process.

Background technique

The design of the invention is based on the practical technology of comprehensive utilization of mineral resources and prevention and control of environmental pollution, and is a sorting device and process flow for removing unburned residual carbon in fly ash by using a high-voltage electrostatic field. As a product of pulverized coal combustion, fly ash is affected by raw materials and combustion conditions, and the undisturbed ash will more or less contain unburned organic matter, that is, unburned residual carbon. The excessive unburned carbon content in fly ash not only brings corresponding environmental problems, but also restricts the application of fly ash in many fields.

The total annual discharge of fly ash in the world is more than 500 million tons. And our country is more than 100 million tons, ranking second in the world. With the development of my country's economic construction, the discharge of fly ash will further increase, which will bring more environmental problems accordingly. Therefore, the economical and effective comprehensive utilization of fly ash has increasingly become an important issue. However, one of the main problems encountered in the process of resource utilization of fly ash is that the content of unburned carbon exceeds the standard, which restricts the application of fly ash in many fields. For example, in building materials and road filling, excessive carbon content in fly ash will significantly affect the water absorption and stability of building and filling materials, and have a significant negative impact on the effective comprehensive utilization of fly ash. Therefore, only by reducing the carbon content of fly ash can its quality level be effectively improved, thereby opening up a broad market for its comprehensive utilization.

There are two main ways to reduce the carbon content of fly ash in the world today: 1. Reduce the carbon content before ash discharge, that is, carry out boiler transformation to improve the combustion efficiency of pulverized coal; 2. Use certain techniques and methods for high-carbon fly ash, Remove part of the unburned charcoal. The main practical technologies are: combustion method, electric separation method, flotation method and centrifugal separation, etc. Among them, the flotation method of wet separation and the electric separation method of dry separation are the most commonly used.

At present, the high-carbon fly ash flotation process is developed from the coal one-stage flotation process. For example, the carbon content of raw ash from the power plant of Gansu Baiyin Company is about 35% on average. After flotation, the carbon content is reduced to less than 5% (Shao Jingbang, Wang Zune. Ways to reduce the carbon content of fly ash. China Coal, 1998, 24. (10): 17-19.). However, due to the adsorption of organic oil compounds on the surface of fresh coal particles, it shows strong natural hydrophobicity; while fly ash is produced at a temperature as high as 1500 ° C, and its natural hydrophobicity is poor. Therefore, the carbon particles in fly ash are different from unburned coal. And because there are various factors of wide-level feed in the first-stage flotation process that interfere with each other, and the optimal configuration cannot be achieved under the same operating conditions and reagent system. Therefore, this fly ash flotation process based on the coal flotation process has the disadvantages of unsatisfactory decarbonization and separation indicators and low separation efficiency. In addition, the activity of fly ash after wet treatment will decrease, and it will also increase the cost of product dehydration and drying. However, the products separated by dry separation methods such as electric separation do not need to be filtered and dried, and the products have good activity. With the advancement of technology, dry electrostatic deposition has become dominant, and power plants are increasingly using dry separation to process the carbon in fly ash (Jiao Youzhou, Zhang Quanguo, Zhang Xiangfeng, etc. The electrical characteristics of fly ash and Experimental research on friction high-voltage electrostatic decarbonization technology. Journal of Henan Normal University (Natural Science Edition), 2004, 32(3): 36-40).

There are two kinds of dry processing of fly ash in thermal power plants: wind separation and electric separation. Among them, the air separation method is based on wind classification and centrifugal classification, and is mainly used to improve the fineness of fly ash, but it is powerless for the carbon in it; The role of the centrifugal field of the decarbonizer increases the fineness of fly ash while decarbonizing (Gong Wenyong; Zhang Hua. Research on decarbonization technology of fly ash by electric separation. Fly Ash, 2005, (3): 33～36 ).

Previously, electric separation was used for the separation of carbon and ash in boiler fly ash. People have carried out extensive research and achieved a number of satisfactory results. However, the research and application has not been reported yet.

The parallel plate electrostatic separator and the triboelectric electrostatic field separation process have a particularly good separation effect on fine particle materials such as high-carbon fly ash, taking into account the separation accuracy and yield, and are internationally advanced. Horizontal electrostatic field separation equipment and process.

Contents of the invention

The purpose of the present invention is to provide a parallel plate electrostatic separator for fly ash decarbonization and a triboelectric electrostatic field separation process, which solves the corresponding environmental problems caused by excessive residual carbon content in fly ash and the fly ash To solve the problem of comprehensive utilization, a low-cost, simple process and high efficiency device and process for fly ash electric separation and carbon removal are proposed.

The structure diagram of the parallel-plate electrostatic separator of the present invention is shown in Figure 1. The parallel-plate electrostatic separator consists of three parts: a guide 2, a high-voltage electrostatic separation chamber 6 and a product separation chamber 7. The guide 2 is a seamless steel pipe inserted from the upper end of the electrostatic separator, fixed by arc welding; the cross section of the high-voltage electrostatic separation chamber is rectangular, and its front and rear walls are composed of metal plates 3 and 4, wherein the metal plate 3 is connected to the negative high voltage generator The metal plate 4 is grounded, and a high-voltage uniform gradient electric field is generated between the two metal plates after power-on; the product compartment 7 is located at the bottom of the entire parallel-plate electrostatic separator, and is connected to the high-voltage electrostatic separation chamber 6 through a flange 12 . Two partitions 8 are installed in the longitudinal direction of the product compartment. The upper part of the partition 8 (the part above the flange) is a movable partition. By changing its inclination angle, the gap h1 and h2 of the partition can be adjusted to control Yield and grade of each product. A high-voltage uniform gradient electric field is generated between two metal plates; material particles with different positive and negative charges will produce material stratification under the action of the high-voltage electric field; the material laminar flow will enter the product compartment with the carrier gas, and in the compartment The center is separated by a partition to form a stream of concentrate and tailings.

The electrostatic separation process of the present invention consists of three parts: a feeding system, a parallel plate electrostatic separation system, and a product collection system. The core separation device is a parallel plate electrostatic separator, which, together with corresponding feeding and product collection equipment, forms a complete triboelectric electrostatic field separation process system to remove unburned carbon particles in fly ash. This sorting process is a dry physical sorting process, no slurry preparation is required, no waste water is produced, and no dehydration and filtration devices are required. Therefore, compared with wet separation processes such as flotation separation, the process is simple and the operation cost is low.

The feeding system is mainly composed of an electromagnetic vibrating feeder and a pneumatic transmission pipeline to form a fly ash dry powder material feeding system; the dry powder material is sorted by a parallel plate electrostatic separator to obtain coal-fired fly ash, residual carbon particles and Three kinds of separation products of intermediate materials; coal-fired fly ash products and residual carbon particle products are collected by the product collection device composed of cyclone and bag collector, and the final fly ash products and residual carbon products are obtained respectively. The intermediate product is returned to the parallel plate electrostatic separator for reselection.

Description of the process flow of fly ash residual carbon triboelectric electrostatic field separation:

In conjunction with accompanying drawing 2, the working process of this fly ash residual carbon triboelectric electrostatic field sorting process is described as follows:

The raw material of fly ash is fly ash from coal-fired thermal power plants, the maximum particle size of which is not more than 2.0 mm, and the residual carbon content is between 5% and 40%. First, the fly ash dry ash feed 13 is fed into the feed hopper 14, and the buffer time of the feed hopper 14 is 1 to 5 minutes; then it is transported to the pneumatic conveyor receiving hopper 16 through the electromagnetic vibration feeder 15 to form a pneumatic conveyor The buffer time of feeding 17 and receiving hopper 17 of the pneumatic conveyor is 1 to 5 minutes; the purpose of setting feeding hopper 14 and receiving hopper 16 is to ensure the continuity and stability of production. During the conveying process of the electromagnetic vibrating feeder, the fly ash material is charged by friction with the Teflon material lining the conveyor. Among them, the carbonaceous component is positively charged, while the inorganic component is negatively charged; the carrier gas of the pneumatic conveyor is provided by the blower 18, and after the carrier gas 19 is input into the pneumatic conveyor 20, it is fed with a receiving hopper, together with the underflow 29 of the intermediate product Form the electrostatic separator feeding material 1. The concentration (gas-solid ratio) and flow rate of the feed material 1 of the electrostatic separator are jointly determined by the vibration frequency of the electromagnetic vibrating feeder 15 and the blowing volume of the blower 18. The concentration range of the feed 1 of the electrostatic separator is 12-27wt.%, and the flow rate is controlled between 1120-1860Nm ³ /h. The throughput of the whole sorting system is 3000-5500kg/hr.

After the electrostatic separator feed 1 with different charges is blown into the electrostatic separator 23, after the charged electrostatic separator feed 1 is blown into the parallel plate electrostatic separation chamber 6 through the guide 2, the The material particles are subjected to Coulomb forces in different directions in the high-voltage electric field. Among them, the positively charged carbon residue particles are attracted to the direction of the negative plate, forming a material laminar flow rich in carbonaceous particles; while the negatively charged fly ash particles are attracted by Attract to the opposite direction to form a laminar flow of material rich in fly ash particles; the layered material flow will enter the product compartment 7 with the carrier gas, and be separated by the partition 8 in the compartment; adjust the two partitions The gaps h1 and h2 can control the yield and grade of fly ash stream 9, intermediate stream 10 and residual carbon stream 11. Through the separation of the high-voltage electrostatic field, the gas-solid two-phase flow of fly ash, the gas-solid two-phase flow of residual carbon and the gas-solid two-phase flow of intermediate products are formed.

The product collection device is composed of a cyclone 25 and a cloth bag collector 26; the residual carbon gas-solid two-phase flow 11, the fly ash gas-solid two-phase flow 9 and the intermediate material gas-solid two-phase flow separated by the electrostatic separator 23 10. After being pressurized by the cyclone feeding blower 24, it is fed into the cyclone 25; through the concentration of the cyclone, the underflow product (with a particle size of 10-500 μm) produced is separated from the gas and solid by the bag collector 26, The final solid fly ash product 27 and residual carbon product 28; the cloth bag collector 26 is a double-circuit design, that is, the gas-solid separation is carried out all the way, and the material is unloaded all the way, and the two working processes are carried out alternately to ensure the continuity of the entire product collection process; The underflow 29 of the intermediate product does not go through the gas-solid separation of the bag collector, and directly returns to the electrostatic separator feeding 1 to re-select the intermediate material; the overflow 30 of each cyclone directly returns to the inlet of the blower 6 to form a blower. Inflow 22, the overflow particle size is controlled at 0.0125-10 μm, which is controlled by adjusting the insertion depth of the cyclone overflow pipe and the air volume of the cyclone feeding blower 24 during operation.

Advantage or positive effect of the present invention:

The parallel plate electrostatic separator and the matching triboelectric electrostatic field separation process are used to separate the unburned net residual carbon in the fly ash. The separation results show that the parallel plate electrostatic separator and triboelectric electrostatic field separation process can effectively remove residual carbon in fly ash. The parallel plate electrostatic separator not only has less investment and power consumption, but also has a small amount of maintenance and low operating costs; compared with wet separation processes such as flotation separation, the dry physical separation process is significantly simplified. There is no need for pulp preparation and chemical addition, no waste water generation, and no dehydration filter device. Therefore, there is basically no harm to the surrounding environment. Its process cost is better than other processes such as flotation separation.

Description of drawings

Figure 1 is a parallel plate electrostatic separator of the present invention. Among them, electrostatic separation chamber feed 1, guide 2, high voltage negative plate 3, grounding plate 4, negative high voltage generator 5, parallel plate electrostatic separation chamber 6, product compartment 7, partition 8, fly ash flow 9. Intermediate stream 10, carbon residue stream 11, flange plate 12, guider insertion depth h, distance h1 between the separator and the high-voltage negative plate, and distance h2 between the two separators.

Fig. 2 is the triboelectric electrostatic field sorting process flow of the present invention. Among them, electrostatic separator comprehensive feeding 1, fly ash raw ash feeding 13, feeding hopper 14, electromagnetic vibration feeder 15, receiving hopper 16, pneumatic conveyor feeding 17, pneumatic conveyor blower 18, carrier gas 19. Pneumatic conveyor 20, electrostatic separator feed 21, electrostatic separator overflow feed 22, parallel plate electrostatic separator 23, cyclone feed blower 24, cyclone 25, cloth bag collector 6, powder Coal ash product 27, carbon residue product 28, intermediate product 29, cyclone overflow 30.

The capacity of the feeding hopper and the receiving hopper is the processing capacity of the entire electrostatic separation system for 1 to 5 minutes. The length of the Teflon charged coating on the electromagnetic vibrating feeder is 100 cm. The cloth bag collector is a double-circuit design, that is, one for gas-solid separation and one for unloading. The two working processes are carried out alternately. The model is selected according to the actual processing capacity and filtration pressure in the application. The insertion depth of the cyclone overflow pipe for each product can be adjusted. The pneumatic conveyor blower and each cyclone feeding blower are general fluid machines, and their selection can be made according to the actual flow rate and pressure rise.

Detailed ways

Here, the present invention is further illustrated by examples. Two kinds of fly ash raw ash from a certain coal-fired power plant in Shaanxi are selected, which are characterized by a high loss on ignition index (8%-25%). Sorting is carried out by using the triboelectric electrostatic field sorting process shown in the accompanying drawing.

Table 1 The chemical composition and ignition loss of the two kinds of fly ash used SiO _{2 Fe2O3 _} Al ₂ O ₃ CaO MgO SO ₃ Loss on ignition fly ash 1 48.08 4.69 39.22 2.59 1.14 0.55 9.17 fly ash 2 46.92 5.24 39.37 2.71 0.76 0.27 16.03

Operating process and conditions

The guide for the parallel plate electrostatic separator used had an inner diameter of 80 mm and an insertion depth h of 125 mm. First turn on the 2.1kV negative high voltage generator power supply to make the electrostatic separation chamber generate a high voltage electric field with a field strength of 200kV/m. And start the blower of each product to make the electrostatic separator system enter the working state. Then start the feeding system: first turn on the carrier gas blower of the pneumatic conveyor, and blow air to the pneumatic conveyor. After the air pressure of the blower is stable, start the electromagnetic vibrating feeder again. The raw material fly ash comes from the electrostatic precipitator of the coal-fired power plant and is directly fed into the feeding hopper without any treatment. Adjust the air volume of the blower and the vibration frequency of the electromagnetic vibrating feeder to keep the feeding concentration of the electrostatic separator at 21wt.%, and the flow rate at 1510Nm ³ /h. The throughput of the whole sorting system is 4630～5120kg/hr.

Under the action of the high-voltage electric field of the electrostatic separator, the material produces a stratified flow, and enters the compartment with the carrier gas, and is separated by the partition in the compartment. According to the product yield and grade requirements of fly ash and residual carbon, adjust The gap between the two partitions to meet the index requirements. Through the concentrating action of the cyclone, the underflow product produced is separated from the gas and solid through the bag collector to obtain solid fly ash products and residual carbon products.

For two kinds of raw fly ash from a coal-fired power plant in Shaanxi, the specific separation conditions and operating parameters of this triboelectric electrostatic field separation process are shown in Table 2.

Table 2 The specific separation conditions and operating parameters of the electrostatic separation system for the two types of fly ash Feed flow rate of electrostatic separator Nm3/h Feed concentration of electrostatic separator wt.% charged material Negative high voltage generator voltage kV High voltage electric field strength kV/m Partition partition spacing h1cm Partition partition spacing h2cm Handling capacity of sorting system kg/hr fly ash 1 1510 twenty one Teflon 2.1 200 11.7 5.6 5120 fly ash 2 1510 19 Teflon 2.1 200 12.9 4.7 4630

sorting result

The triboelectric electrostatic field separation process system performs electrostatic separation of fly ash 1 and fly ash 2 under the above operating parameter conditions, and the separation indexes are shown in Table 3 and Table 4.

Table 3 Separation index of fly ash 1 (yield, ash recovery, moisture, ash and loss on ignition) by the triboelectric electrostatic field separation system Raw materials and products Yield Ash recovery moisture Ash Loss on ignition raw material gray 100 100 0.94 90.83 9.17 Fly Ash Products 61.7 64.63 0.59 95.66 4.34 Carbon residue products 34.83 32.56 1.17 85.37 14.63

Table 4 Separation indicators of fly ash 2 (yield, ash recovery, moisture, ash and loss on ignition) by the triboelectric electrostatic field separation system Raw materials and products Yield Ash recovery moisture Ash Loss on ignition raw material gray 100 100 0.81 83.97 16.03 Fly Ash Products 55.78 57.82 0.66 94.59 5.41 Carbon residue products 42.49 36.93 1.23 79.41 20.59

It can be seen that the loss on ignition of fly ash 1 and fly ash 2 has dropped from 9.17% and 16.03% to 4.34% and 5.41%, respectively, reaching the national standard GB 1596-9 Class I ash and Class II ash standards, and also reached the U.S. Class C gray standard of ASTM C-6181. Among them, the gap between the partitions has a significant control effect on the recovery of carbon residue. The separation results show that the triboelectric electrostatic field separation process can effectively remove residual carbon in fly ash. Compared with wet separation processes such as flotation separation, the decarbonization separation index and separation efficiency of this process flow Ideally, there is no need for slurry preparation and chemical addition, no waste water, and no need for dehydration and filtration devices. Therefore, not only the investment is small, but also the operating cost is low, and there is basically no harm to the surrounding environment. Its process cost is better than other processes such as flotation separation.

Claims (5)

1, a kind of parallel plate electrostatic separator of fly ash charcoal-removing is made up of guide, high-pressure electrostatic separation chamber, product compartment (7) three parts; It is characterized in that wall is made of two parallel metal sheets with different electric charges before and after the high-pressure electrostatic separation chamber, wherein, metallic plate (3) connects negative high-voltage generator, and metallic plate (4) ground connection produces the even gradient electric field of high pressure between these two metallic plates; Product compartment (7) is in the below of whole parallel plate electrostatic separator, is connected with high-pressure electrostatic separation chamber (6) by ring flange (12); Longitudinal direction in the product compartment is equipped with two separates dividing plate (8), and the top of separating dividing plate (8) is active clapboard, by changing its angle of inclination, adjusts spacer gap h1 and h2, controls the productive rate and the grade of each product.

2, the described separator of a kind of use claim 1 carries out friction charged electrostatic field sorting process, it is characterized in that, is made of feeding system, parallel plate electrostatic piece-rate system, product gathering system three parts; Powdered coal ash is the flyash of coal-fired station, and at first, flyash dry ash pan feeding (13) feeds in the feed hopper (14), and the buffer time of feed hopper (14) is 1～5 minute; With after electro-vibrating feeder (15) is delivered to pneumatic transfer device hopper (16), form pneumatic transfer device pan feeding (17), be 1～5 minute between the buffer time of pneumatic transfer device hopper (16); The flyash material with the teflon material friction of conveyer liner, and is with electric charge in the course of conveying of electro-vibrating feeder; Wherein, the carbonaceous component is positively charged, and inorganic component is electronegative; The carrier gas of pneumatic transfer device is provided by air blast (18), behind carrier gas (19) the input pneumatic transfer device (20), carries acceptance and struggles against pan feeding and form electrostatic separator pan feeding (21); The gas-solid ratio concentration of electrostatic separator pan feeding (21) and flow are by the collaborative decision of the blow rate required of electro-vibrating feeder (15) vibration frequency and air blast (18); After being blown into electrostatic separator (23) with the comprehensive pan feeding of the electrostatic separator of different electric charges (1), at first after guide (2) is blown into parallel plate electrostatic separation chamber (6), with the material particles of positive and negative different electric charges therein high voltage electric field in be subjected to the Coulomb force of different directions, wherein, positively charged char particle is attracted to the negative plate direction, forms the material laminar flow that is rich in the carbonaceous particle; And electronegative fly ash granule is attracted to opposite direction, forms the material laminar flow that is rich in fly ash granule; The layering material flow can enter in the product compartment (7) with carrier gas, is separated dividing plate (8) and separates in compartment; By adjusting gap h1 and the h2 that separates dividing plate, the productive rate and the grade of control flyash Dual-Phrase Distribution of Gas olid (9), the Dual-Phrase Distribution of Gas olid (10) of middle material and carbon residue Dual-Phrase Distribution of Gas olid (11).

3, in accordance with the method for claim 2, it is characterized in that feeding system is by electro-vibrating feeder, and cooperation pneumatic transfer pipeline, forms flyash dry material feeding system; Dry material obtains burned-coal fly ash, char particle and three kinds of products of separated of intermediate material after the parallel plate electrostatic separator sorting; The capture of the product gathering-device that burned-coal fly ash product and char particle product are formed by cyclone and cloth bag gatherer obtains final flyash product and carbon residue product respectively; Intermediate products then return the parallel plate electrostatic separation chamber and select.

4, in accordance with the method for claim 2, it is characterized in that the product gathering-device is made of cyclone (25) and cloth bag gatherer (26); Carbon residue, flyash and intermediate material Dual-Phrase Distribution of Gas olid by electrostatic separator (23) sorting obtains after cyclone pan feeding air blast (24) pressurization, feed cyclone (25); By the inspissation of cyclone, the generation granularity is that the underflow product of 10～500 μ m carries out gas solid separation by cloth bag gatherer (26), last solid-state flyash product (27) and carbon residue product (28); Cloth bag gatherer (26) designs for the double loop, and one the tunnel carries out gas solid separation, one tunnel discharging, and two courses of work hocket, to guarantee the continuity of entire product collection process; The underflow of intermediate products (29) directly is back to electrostatic separator pan feeding (1) intermediate material is selected again then without cloth bag gatherer gas solid separation; Each cyclone overflow (30) then directly is back to air blast (18), form air blast become a mandarin (22), overflow granularity is controlled at 0.0125～10 μ m, controls by the insertion depth of adjustment cyclone overflow pipe and the air quantity of cyclone pan feeding air blast (24) in the operation.

5, in accordance with the method for claim 2, it is characterized in that the particle maximum particle size of described flyash is no more than 2.0mm, carbon residue content is between 5%～40%; The concentration range of described electrostatic separator pan feeding (1) is 12～27wt.%, and flow-control is at 1120～1860Nm ³Between/the h.The treating capacity of whole separation system is 3000～5500kg/hr.

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